Well, they still have a while in Unova. They've yet to introduce Cheren (if even possible), and they've totally blew off Team Plasma, so that's going to be a series of episodes that most likely will lead up to the release of the Eeveelution movie, meaning Virgil probably would continue to aid them on their journey.
Not to mention that there is still, and always, episodes after Ash looses at the Pokemon leagues.
As for Best Wishes, I know that's the name of the season, but I'm pretty sure that already occurred. Don't take my word on any of this, though. Just info from what I know.